1. Field of Disclosure
The present disclosure relates to a gear train and more particularly to a transmission system for driving a generator or generators.
2. Related Art
A typical application for a transmission system is for use in wind power generating systems, including wind turbine technology. Wind turbine technology has become increasingly demanding as requirements for twenty or thirty years of life, with greater reliability, is being required. In a typical wind turbine, the turbine rotor is rotated at relatively slow speeds as wind impinges on an arrangement of expansive, radially positioned wind blades. It should be appreciated that the torque acting on the gear arrangement is large. In addition, at the base of the rotating wind blades, the loads can vary greatly and may be high, for sometimes over prolonged periods of time, and under varying speeds. In order to function reliably, it is usually critical that the gear arrangement be capable of performing under these demanding conditions.
Typical gear arrangements generally require a large number of bearings to operate properly. Some manufacturers may use direct drive systems in an attempt to eliminate extra bearings and gears. In some designs, offered in either an epicyclical single planetary arrangement, or a compound differential planetary arrangement, the designer typically begins from the outside, larger size, first stage, gearing. This makes it possible to increase the arm length and use only three planets to drive a smaller output center pinion to increase the rotational speed of the output shaft. The output shaft is connected typically using splines or a similar arrangement to a shaft which drives a generator.
Since gear arrangements typically require a large number of bearings to operate properly, the more bearings used in the gearing arrangement, the more likely is that one or more of the bearings will fail. Generally, the failure in the gear arrangement of many wind turbines, for example, is due to failure of bearings in this unusually demanding bearing environment. Thus it is advantageous to reduce the number of bearings needed in any gear arrangement.